1. Field of the Invention
The present invention relates to a disk playback apparatus for reproducing video and audio in response to data recorded on a video CD (Compact Disk), and more particularly to a technique for synchronizing the audio to the video.
2. Description of Related Art
Conventionally, a disk playback apparatus for reproducing video and audio in response to the data recorded on a video CD has been known. The video CD played back by the disk playback apparatus stores the video and audio data by dividing them into units called packets. During playback of the video and audio in response to the data recorded on the video CD, the disk playback apparatus stores addresses (track address and sector address) recorded on the video CD containing a packet while updating the addresses.
It is very common for a user of the disk playback apparatus to stop the playback of the video and audio, followed by restarting the playback again (called “continued playback” from now on). In this case, the disk playback apparatus reads the packet from the address where the playback stops, and carries out the continued playback.
As for relevant techniques, Relevant Reference 1 discloses a timing detecting circuit and method for detecting the processing timing of frame data corresponding to playback output time management information for synchronization control between pictures and audio. The timing detecting circuit has a counter, a register and a frame counter in a video decoder. The counter counts the number of frames of encoded picture data stored in the frame memory area of a RAM. The register loads the count value from the counter in response to the timing at which a PTS (Presentation Time Stamp) is supplied from a demultiplexer to a host processor, and decrements the loaded count value every time the analyzing processing is completed which is performed frame by frame for the encoded picture data read from the storing area. The frame counter has a “0” detecting circuit output a timing detection signal when the count value of the register becomes zero. The configuration not only enables the compatibility with conventional apparatuses, but also has an advantage in cost.
As an alternative technique, Relevant Reference 2 discloses a disk playback apparatus and a disk playback method capable of facilitating the handleability of a user by automatically switching the types of a sub-video stream on a specified unit basis. To playback a disk recording a main video and multiple types of sub-videos corresponding to the main video, the technique specifies two or more types of the sub-videos, and carries out the playback by automatically switching the designated two or more types of the sub-videos sequentially at every specified playback unit.
Relevant Reference 1: Japanese patent application laid-open No. 9-18870/1997.
Relevant Reference 2: Japanese patent application laid-open No. 2001-344873.
Such video CDs are roughly divided into common CDs recording motion pictures and audio, and slide show CDs recording still pictures and audio. The common CDs contain an overwhelming amount of picture data as compared with the audio data in the playback data. Accordingly, when the continued playback is performed from the address memorized at the stop of the playback, it is very likely that the video is played back first, and then the audio, thereby providing a quite normal feeling.
In contrast with this, as for the slide show CDs, the picture data occupy an extremely small amount of data compared with the audio data in the playback data, and are sparse in the playback data. Accordingly, when the continued playback is performed from the address memorized at the stop of the playback, it is very likely that the audio is almost always played back first, and then the video. Thus, a state occurs in which although the audio is being output, the video is not yet output, presenting a problem of providing a sense of incongruity.